Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/001—Interlayers, transition pieces for metallurgical bonding of workpieces
  • B23K35/004—Interlayers, transition pieces for metallurgical bonding of workpieces at least one of the workpieces being of a metal of the iron group
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/005—Ferrite

Definitions

• the present invention relates to a ferritic stainless steel (ferritic stainless steel) which is excellent in corrosion resistance (corrosion) resistance) of the welded portion with austenitic stainless steel (austenitic stainless steel) and excellent in surface properties (surface quality) among corrosion resistances. Is.
• austenitic stainless steel SUS304 (18% Cr-8% Ni) (Japanese Industrial Standard, JIS G 4305) is widely used due to its excellent corrosion resistance.
• this steel type is expensive because it contains a large amount of Ni.
• stainless steel described in Patent Document 1 has been developed as a steel type having excellent corrosion resistance equivalent to SUS304.
• Patent Document 1 as component composition, C: 0.03% or less, Si: 1.0% or less, Mn: 0.5% or less, P: 0.04% or less, S: 0.02% or less, Al: 0.1% or less, Cr: 20.5% or more, 22.5% or less, Cu: 0.3% or more, 0.8% or less, Ni: 1.0% or less, Ti: 4 ⁇ (C % + N%) or more, 0.35% or less, Nb: 0.01% or less, N: 0.03% or less, C + N: 0.05% or less, the balance being Fe and inevitable impurities
• a stainless steel sheet is disclosed.
• ferritic stainless steels such as JIS-SUS444 and JIS-SUS430J1L are also less sensitive to stress corrosion cracking (Stress Corrosion Cracking) than austenitic stainless steel, and do not contain Ni, which has a large price fluctuation. It is widely used as a material for automobile exhaust system members, water tanks, and construction materials.
• austenitic stainless steel is used for difficult-to-work parts that cannot be molded with ferritic stainless steel.
• a welding method TIG welding (Tungsten Inert Gas welding) is mainly used, and good corrosion resistance is required for the welded portion as well as the base material. It is done.
• the ferritic stainless steel disclosed in Patent Document 1 has good corrosion resistance in welded parts of the same steel type.
• the corrosion resistance of the welded part may be lower than that of the base material.
• the corrosion resistance of the welded portion is determined by the thermal history during welding, in which C and N in the steel are combined with Cr to form Cr carbide (Cr 23 C 6, for example), or Cr nitride (Cr- (precipitates at the grain boundaries) as nitrides) (CrN 2 etc.), resulting in a so-called sharpness caused by a Cr depletion layer having a lower Cr concentration than the base material at the grain boundaries. This is due to sensitization and deterioration of its corrosion resistance.
• Ti and N in the molten steel may react during solidification to precipitate as TiN.
• This TiN is poor in ductility at high temperature, and becomes a surface flaw in the hot rolling process and deteriorates the surface properties.
• the scratches generated in this way are deep and will not disappear even after hot-rolled sheet annealing (acidal pickling), subsequent cold rolling, cold-rolled sheet annealing, pickling, etc.
• the present invention has been made in view of such circumstances, and an object of the present invention is to provide a ferritic stainless steel which is excellent in corrosion resistance of a welded portion and excellent in surface properties even when welded to austenitic stainless steel.
• the present inventors have developed the corrosion resistance of the base metal part and the welded part and the surface defects of the steel sheet (scab, pin hole, pin scab, linear scab, Through careful investigation and examination of the influence of the chemical composition of steel on the occurrence of titanium stringer shape anomalies and white stripe pattern color defects, the following findings were obtained. (1) By optimizing the concentration of the ferrite phase promoting element, the so-called ferrite former element, the structure of the welded portion between the austenitic stainless steel and the ferritic stainless steel is reduced to the C and N solid solubility limit. It should be possible to prevent sensitization to some extent by using a large martensite phase.
• the ferritic stainless steel having excellent corrosion resistance and surface properties of the welded portion according to the above [1], further comprising Al: 0.01% to 0.5% by mass.
• the ferrite having excellent corrosion resistance and surface properties of the welded portion according to the above [1] or [2], further comprising Sb: 0.05% to 0.30% by mass% Stainless steel.
• the ferritic stainless steel of the present invention is suitable for kitchen equipment, building interior materials, industrial machinery, automobile parts and the like because it is excellent in corrosion resistance and surface properties of the welded portion even when welded with austenitic stainless steel.
• C 0.003-0.012%
• C is easy to combine with Cr to form Cr carbide, and when Cr carbide is formed in the heat-affected zone during welding, it causes intergranular corrosion. Therefore, C is preferably as low as possible. Therefore, C is set to 0.012% or less. On the other hand, even if it is too low, a great amount of time is required for refining, so the C content is in the range of 0.003 to 0.012%. Preferably, it is in the range of 0.003 to 0.010%.
• Si 0.30 to 0.60% Si is an important element in the present invention.
• Si the solubility product of Ti and N in the molten steel is lowered, and precipitation of the Ti nitrocarbon compound is promoted at a high temperature before columnar crystals are formed.
• N in the molten steel is lowered, and TiN is less likely to precipitate at the columnar grain boundaries during the subsequent columnar crystal growth.
• Si by adding 0.30% or more of Si, it is possible to suppress the precipitation of TiN on the columnar crystal grain boundaries that cause titanium stringer defects.
• the Si amount is in the range of 0.30 to 0.60%. Preferably it is 0.40 to 0.50% of range.
• Mn 0.10 to 0.35% Since Mn has a deoxidizing action, 0.10% or more is added. Further, since it is an austenite phase promoting element (austenite former element), it promotes the formation of a martensite phase in a welded portion (hereinafter referred to as a different steel type welded portion) with austenitic stainless steel. However, it combines with S present in the steel excessively to form MnS, which is a soluble sulfide, and lowers the corrosion resistance. Therefore, the Mn content is in the range of 0.10 to 0.35%. Preferably it is 0.10 to 0.25% of range.
• P 0.040% or less
• P is an element harmful to corrosion resistance. Furthermore, it is an element that reduces hot workability. In particular, these tendencies become prominent when it exceeds 0.040%. For this reason, the amount of P is made into 0.040% or less. Preferably it is 0.030% or less.
• S 0.020% or less S is an element harmful to corrosion resistance.
• MnS MnS is formed, which becomes a starting point of pitting corrosion and deteriorates corrosion resistance. Such an effect becomes remarkable when it exceeds 0.020%.
• the amount of S is made into 0.020% or less.
• it is 0.010% or less. More preferably, it is 0.006% or less.
• Cr 17.0 to 19.0% Cr is an element indispensable for forming a passive film on the surface of stainless steel and increasing the corrosion resistance of the base material. In order to obtain good corrosion resistance, addition of 17.0% or more is necessary, but addition exceeding 19.0% prevents martensite from being formed in a dissimilar steel type weld with SUS304 and prevents deterioration of corrosion resistance. Disappear. For this reason, the Cr content is in the range of 17.0 to 19.0%. Preferably it is 17.5 to 18.5% of range.
• Ni Over 0.10% to 0.30% Ni is an element that contributes to improvement of crevice corrosion resistance. Furthermore, since it is an austenite phase promoting element (austenite former element) like Mn, it promotes the formation of the martensite phase in the welded zone of different steel types. However, when added over 0.30%, SCC sensitivity increases. It is also an expensive element. For this reason, the Ni content is in the range of more than 0.10% to 0.30%. Preferably it is 0.20 to 0.30% of range.
• Nb 0.005% to less than 0.050%
• a small amount of Nb is also an important factor in the present invention.
• Nb preferentially forms carbonitride over Cr and Ti.
• Nb begins to form carbonitride at a temperature higher than that of Ti in a weld metal and a heat affected zone of a different steel type weld. The reason is not clear, but Ti generates this small amount of Nb carbonitride as a nucleation site in the subsequent cooling process. That is, the formation of Ti carbonitride is promoted by adding a small amount of Nb. Therefore, compared with the case where Nb is not included, the ability to fix C and N by the molten pool of the different steel type welded portion and Ti of the heat affected zone is increased.
• the Nb amount is set to 0.005% or more.
• the recrystallization temperature of the cold-rolled sheet is increased, and in order to obtain good mechanical properties, annealing must be performed at a higher temperature than when Nb is not added. You won't get. Therefore, it grows thicker than in the case where the oxide film produced during annealing is not added. For this reason, the pickling property of the cold-rolled sheet in the high-speed pickling method used in the carbon steel manufacturing facility described above is deteriorated and the productivity is lowered. Therefore, the Nb content is set to a range of 0.005 to less than 0.050%. Preferably it is 0.01% or more and less than 0.050% of range.
• Ti 0.10 to 0.40% Ti must be added in an amount of 0.10% or more in order to ensure the corrosion resistance of a welded part of a different steel type with austenitic stainless steel (to prevent sensitization). However, if added over 0.40%, TiN is formed at the columnar grain boundaries, the titanium stringer defects become stronger, and the surface of the hot rolled annealed pickled plate must be ground with a grinder to obtain good surface quality. I will have to. For this reason, the Ti amount is set to a range of 0.10 to 0.40%. Preferably it is 0.20 to 0.40% of range.
• Mo 0.20% or less
• Mo is an element that strengthens the passivation film and significantly improves the corrosion resistance, and the effect is obtained by adding 0.01% or more.
• Mo is a ferrite phase promoting element, a so-called ferrite former element, and if added over 0.20%, the welded zone of the different steel type with the austenitic stainless steel does not become martensite, and the solid solution amount of C and N Therefore, it becomes impossible to prevent sensitization. Therefore, Mo is 0.20% or less.
• Mo since Mo also reduces the toughness of a hot-rolled sheet, it is preferably 0.10% or less.
• N 0.005 to 0.015%
• N is likely to combine with Cr to form Cr nitride.
• Cr nitride When Cr nitride is formed in the welded zone and the heat-affected zone during welding, it causes grain boundary corrosion, so N is preferably as low as possible.
• the N content is in the range of 0.005 to 0.015%.
• the content is 0.005 to 0.012%.
• Cu 0.3% to 0.5%
• Cu is an element that enhances corrosion resistance, particularly corrosion resistance when an aqueous solution or weakly acidic water droplets adhere. This is presumed that Cu dissolves at a certain electrochemical potential in an aqueous solution or weakly acidic water droplets, and Cu reattaches to the base iron to suppress dissolution resistance.
• the Cu amount is set in the range of 0.3 to 0.5%. Preferably it is 0.3 to 0.4% of range.
• Mg Less than 0.0005% Mg is an impurity mainly mixed from bricks in the converter. Mg becomes the starting point of a wide variety of inclusions, and even if the amount is mixed, it becomes a nucleation site for other inclusions, and it is difficult to re-dissolve even if annealing is performed, hot-rolled annealing pickling plate, cold-rolling annealing pickling Deteriorates the surface properties of the plate. Therefore, the Mg content is less than 0.0005%. Preferably it is less than 0.0003%.
• the above are the basic chemical components of the present invention, and the balance consists of Fe and inevitable impurities.
• Al and Sb may be added as selective elements.
• Zr and V may be added as selective elements for the purpose of improving the corrosion resistance of the different steel type welds.
• Ca 0.0020% or less is acceptable.
• Al 0.01 to 0.5% Al needs to be added when the gas shield for TIG welding is insufficient.
• TIG welding welding is generally performed by shielding the rear surface and the front surface with gas.
• the shield is not sufficient, and N in the atmosphere is mixed into the molten pool, exceeding the solid solution limit of martensite. May not be able to be prevented.
• it is effective to add Al in advance to prevent sensitization. This is because the added Al reacts with N to produce AlN and captures N mixed in the molten pool. This effect can be obtained by adding 0.01% or more.
• the content is preferably in the range of 0.01 to 0.5%. More preferably, it is in the range of 0.1 to 0.5%. More preferably, it is in the range of 0.15 to 0.25%.
• Sb 0.05 to 0.30% Sb, like Al, has an effect of capturing N mixed in from the atmosphere when the gas shield for TIG welding is insufficient, and is an element that should be added in the case of a structure having a complicated shape.
• the Sb content is preferably in the range of 0.05 to 0.30%. More preferably, it is in the range of 0.05 to 0.15%.
• Zr 0.01 to 0.60%
• Zr forms carbonitride preferentially over Cr like Ti and improves corrosion resistance in welds of the same steel type and different steel types, and is an element to be added in consideration of the corrosion resistance of welds.
• Zr is considerably more expensive than Ti, and if added too much, an intermetallic compound is produced, and the toughness of the hot-rolled sheet deteriorates. Therefore, when Zr is added, the Zr content is preferably in the range of 0.01 to 0.60%. More preferably, it is in the range of 0.1 to 0.35%.
• V 0.01 to 0.50%
• V forms carbonitride preferentially over Cr and improves the corrosion resistance of welds of the same steel type and different steel types.
• the effect can be obtained by adding 0.01% or more. However, adding over 0.50% degrades the mechanical properties. Therefore, when V is added, the content is preferably in the range of 0.01% to 0.50%. More preferably, it is in the range of 0.02 to 0.05%.
• a preferred method for producing the steel of the present invention will be described.
• the steel having the above component composition is melted by a known method such as a converter, electric furnace, vacuum melting furnace or the like, and is made into a steel material (slab) by a continuous casting method or an ingot-bundling method.
• the steel material is then heated at 1100 to 1250 ° C. for 1 to 24 hours, or directly hot-rolled to form a hot-rolled sheet without heating.
• the hot-rolled sheet is usually subjected to hot-rolled sheet annealing at 800 to 1100 ° C. for 1 to 10 minutes. However, depending on the application, the hot-rolled sheet annealing may be omitted.
• the hot-rolled sheet after pickling the hot-rolled sheet, it is cold-rolled by cold rolling, and then recrystallized and annealed to obtain a product.
• a reduction rate in thickness of cold rolling can be achieved at a reduction rate of 50% or more in order to obtain good elongation, bendability and press formability, and for the purpose of shape correction. desirable.
• the recrystallization annealing of the cold-rolled sheet is preferably performed at 800 to 950 ° C. from the viewpoint of obtaining good mechanical properties and pickling properties in the case of the 2B product.
• the annealing temperature at this time is 800 Most preferably, it is carried out at ⁇ 900 ° C. Further, it is effective to perform BA annealing (Bright Annealing) for finishing the member where the luster is desired. Further, as described above, it is disadvantageous in terms of cost to further improve the surface properties after cold rolling and after processing, but there is no problem even if polishing is performed.
• Welding voltage 10V
• Welding current 90-110A
• Welding speed 600 mm / min
• Electrode 1.6 mm tungsten electrode
• Shielding gas Front bead side Ar 20 L / min
• Welding speed 600 mm / min
• Electrode 1.6 mm tungsten electrode
• Shielding gas Front bead side Ar 20 L / min
• Welding speed 600 mm / min
• Electrode 1.6 mm tungsten electrode
• Shielding gas Front bead side Ar 20 L / min
• the same specimen was subjected to a corrosion resistance test for a welded portion of a different steel type with SUS304.
• a plate taken from each test material and SUS304 having a thickness of 1.0 mmt were joined by TIG welding, and their surfaces were polished with # 600 abrasive paper, and then examined for corrosion resistance by CCT.
• TIG welding conditions are substantially the same
• the salt spray cycle test was performed by spraying 5% NaCl solution (35 ° C., 2 h) (spraying 5% NaCl aqueous solution at 35 ° C., 2 hr) ⁇ drying (60 ° C., 4 h, relative humidity 20-30%) (drying at 60 °C, 4hr, relative humidity 20 to 30%) ⁇ Wetting (40 °C, 2h, relative humidity 95% or more) .
• Table 2 The results are shown in Table 2.
• the criteria for each test are as follows. (1) Appearance after pickling with cold-rolled annealing: Judged by the ratio of the length of the portion with surface defects to the total length of the plate, the defect rate is less than 5% ⁇ (pass: super good), the defect rate is 5% or more, 10 % (Pass: good), defect rate 10% or more, less than 20% was ⁇ (fail), and defect rate 20% or more was judged as x (fail: very bad).
• Salt spray cycle test results of cold-rolled annealed pickling plate and # 600 polishing plate Rust area after 15-cycle test is less than 10% wrinkle rate ⁇ (pass: super good), 10% or more , Less than 20% was judged as ⁇ (pass: good), 20% or more, less than 30% was judged as ⁇ (failure), and 30% or more was judged as x (failure).
• pickling After being immersed in (sulfuric acid solution) for 120 seconds, pickling is performed by immersing in a mixed acid composed of 15 mass% nitric acid and 3 mass% hydrofluoric acid at a temperature of 55 ° C for 60 seconds. Then, descaling was performed to obtain a hot rolled annealed pickled coil. Further, the steel sheet was then cold rolled to a thickness of 1.0 mm, annealed in a coke oven gas combustion atmosphere with an air ratio of 1.3 at 900 ° C. for 2 minutes, and at a temperature of 80 ° C. and 20 mass% Na 2 SO 4 .
• Corrosion resistance was evaluated by CCT using this cold-rolled annealed pickling plate.
• the surface of the cold-rolled annealed pickling plate was polished with # 600 polishing paper, and corrosion resistance evaluation, welded portion corrosion resistance test, and SUS304 different steel type welded portion corrosion resistance test were performed. Table 4 shows the results obtained as described above.
• the criteria for each test are as follows. (1) Appearance after pickling with cold-rolled annealing: Judged by the ratio of the length of the portion with surface defects to the total length of the plate, the defect rate is less than 5% ⁇ (pass: super good), the defect rate is 5% or more, 10 % (Pass: good), defect rate 10% or more, less than 20% was ⁇ (fail), and defect rate 20% or more was judged as x (fail: very bad).
• Salt spray cycle test results of cold-rolled annealed pickling plate and # 600 polishing plate Rust area after 15-cycle test is less than 10% wrinkle rate ⁇ (pass: super good), 10% or more Less than 20% was judged as ⁇ (passed: good), 20% or more, less than 30% was judged as ⁇ (failed), and 30% or more was judged as x (failed: very bad).
• Corrosion resistance test results for the same steel type welds TIG butt welding between the same steel types, the temper color of the welds was removed with # 600 abrasive paper, and the same steel type welds were welded after 15 cycles of the salt spray cycle test.
• the defect rate is less than 10% ⁇ (pass: super good) 10% or more, less than 20% is ⁇ (pass: good), 20% or more, less than 30% is ⁇ (fail), 30% or more ⁇ (not good) Pass: very bad)
• Corrosion resistance test result of dissimilar steel type welded part with SUS304 After tempering the TIG butt weld with SUS304 and removing the temper color of the welded part with # 600 abrasive paper, the different steel type welded part after 15 cycles of salt spray cycle test , The sprout rate is less than 10% ⁇ (pass: super good) 10% or more, less than 20% ⁇ (pass: good), 20% or more, less than 30% ⁇ (fail), 30% or more ⁇ (Fail: very bad).
• This cold-rolled annealed plate was descaled by performing electrolysis (10 A / dm 2 ⁇ 2 seconds) twice in a solution comprising a temperature of 50 ° C., 15 mass% nitric acid and 0.5 mass% hydrochloric acid, and cold-rolled annealed acid A washboard was obtained.
• Corrosion resistance was evaluated by CCT using this cold-rolled annealed pickling plate. Further, after polishing the surface with # 600 polishing paper, the corrosion resistance was evaluated by CCT, and the TIG welded corrosion resistance test was conducted on the same steel type. In this test, two plates taken from each test material were joined by TIG welding, their surfaces were polished with # 600 abrasive paper, and the corrosion resistance was examined by CCT.
• the TIG welding conditions were as follows, and the welding current was controlled so that the back bead width was 3 mm or more.
• the evaluation surface was a back bead surface.
• Welding voltage 10V
• Welding current 90-110A
• Welding speed 600 mm / min
• Electrode 1.6 mm tungsten electrode
• Shielding gas Front bead side Ar + 20 vol% N 2 20 L / min
• the same specimen was subjected to a corrosion resistance test for a welded portion of a different steel type with SUS304.
• a plate taken from each test material and SUS304 having a thickness of 1.0 mm were joined by TIG welding, and their surfaces were polished with # 600 abrasive paper, and the corrosion resistance was investigated by CCT.
• TIG welding conditions are substantially the same as the above-described welding conditions for the same steel type.
• the salt spray cycle test consists of 5% NaCl solution spray (35 ° C, 2h) ⁇ dry (60 ° C, 4h, relative humidity 20-30%) ⁇ wet (40 ° C, 2h, relative humidity 95% or more) in one cycle. As a result, 15 cycles were performed. The results are shown in Table 6.
• the criteria for each test are as follows. (1) Appearance after pickling with cold-rolled annealing: Judged by the ratio of the length of the portion with surface defects to the total length of the plate, the defect rate is less than 5% ⁇ (pass: super good), the defect rate is 5% or more, 10 % (Pass: good), defect rate 10% or more, less than 20% was ⁇ (fail), and defect rate 20% or more was judged as x (fail: very bad).
• Salt spray cycle test results of cold-rolled annealed pickling plate and # 600 polishing plate Rust area after 15-cycle test is less than 10% wrinkle rate ⁇ (pass: super good), 10% or more Less than 20% was judged as ⁇ (passed: good), 20% or more, less than 30% was judged as ⁇ (failed), and 30% or more was judged as x (failed: very bad).
• Corrosion resistance test results for the same steel type welds TIG butt welding between the same steel types, the temper color of the welds was removed with # 600 abrasive paper, and the same steel type welds were welded after 15 cycles of the salt spray cycle test.
• the defect rate is less than 10% ⁇ (pass: super good) 10% or more, less than 20% is ⁇ (pass: good), 20% or more, less than 30% is ⁇ (fail), 30% or more ⁇ (not good) Pass: very bad) (4) Results of corrosion resistance test of welded part of different steel type with SUS304: TIG butt welding was performed with SUS304, and the temper color of the welded part was removed with # 600 abrasive paper.
• the weld rate after 15 cycles of the salt spray cycle test is less than 10% of the cracking rate ⁇ (pass: super good), 10% or more, less than 20% ⁇ (pass: good), 20% or more, Less than 30% was judged as ⁇ (failed), and 30% or more was judged as ⁇ (failed: very bad).
• Steel grades 23 to 28 and 33 within the scope of the present invention are cold-rolled annealed pickled plates, polished plates, welds of the same grade when the gas shield is insufficient, and SUS304 when the gas shield is insufficient. It was excellent in corrosion resistance and surface properties even in the welded zone of different steel types. In particular, the symbols 25 to 28 and 33 to which Al, Sb, Zr, and V were added were particularly excellent in corrosion resistance even in a dissimilar steel weld with SUS304 when the gas shield was insufficient. On the other hand, Comparative Example No. with a low Cr content of 16.8%. No. 29 had a large rusting area and poor corrosion resistance. Moreover, comparative steel No. with a high Cr addition amount of 19.8%. No.
• the ferritic stainless steel plate having good corrosion resistance of the base metal, corrosion resistance of the same steel type welded portion, corrosion resistance of the different steel type welded portion with SUS304, and surface properties of the cold-rolled annealed pickled plate is hot rolled. It has been clarified that any of the properties that can be obtained without grinding an annealed pickling plate is excellent.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=48535012

Family Applications (1)

Country Status (9)

Cited By (5)

Families Citing this family (8)

Citations (4)

Family Cites Families (7)

• 2012
  • 2012-11-27 CN CN201280059270.9A patent/CN103975086B/zh active Active
  • 2012-11-27 WO PCT/JP2012/007593 patent/WO2013080518A1/ja active Application Filing
  • 2012-11-27 US US14/359,782 patent/US20140294661A1/en not_active Abandoned
  • 2012-11-27 IN IN959KON2014 patent/IN2014KN00959A/en unknown
  • 2012-11-27 KR KR1020147017639A patent/KR20140117370A/ko not_active Application Discontinuation
  • 2012-11-27 EP EP12852604.3A patent/EP2787096B1/en active Active
  • 2012-11-27 ES ES12852604.3T patent/ES2602800T3/es active Active
  • 2012-11-27 JP JP2013546991A patent/JP5713118B2/ja active Active
  • 2012-11-29 TW TW101144674A patent/TWI519652B/zh active

Patent Citations (4)

Non-Patent Citations (4)

Also Published As

Similar Documents

Legal Events